Hitherto, as a process for producing a plastic concrete, there is a well-known process wherein a cement mortar obtained by kneading an aggregate, water, etc., is mixed with a rubber latex of styrene butadiene rubber, nitrile rubber, etc.; a O/W type emulsion of polyvinyl acetate, an epoxy resin, etc.; or a water-soluble polymer such as polyvinyl alcohol, carboxymethyl cellulose, etc., and it is said that the plastic concrete obtained by the aforesaid process is excellent in waterproofing property and has improved bending strength, tensile strength, shock resistance, and abrasion resistance. Furthermore, a resin concrete obtained by consolidating an aggregate with an unsaturated polyester resin, an epoxy resin, etc., is known. However, these concretes have a disadvantage that the specific gravity is generally high. On the other hand, as a process for reducing weight of cement concrete, there are known a process of mixing a cement slurry with a light-weight aggregate and a process of introducing foams into a cement slurry using a foaming agent. As the process of using a foaming agent, there are a process of curing a cement slurry in a foamed state using a surface active agent and a process of mixing a cement slurry with an aluminum powder to cause a chemical reaction of aluminum and the cement and to foam by the hydrogen gas thus generated. In general, a process of using a foaming agent has a large disadvantageous that it is difficult to control the foaming state and thus the foamed state becomes nonuniform. Furthermore, in the case of producing a large concrete body, the foamed state is liable to become coarser in the upper portion thereof than in the lower portion to provide density difference in the concrete body. Also, in general, the size of foams is large, which reduces the appearance of the product. On the other hand, according to the process of using a light-weight aggregate, it is difficult to obtain a high strength light-weight concrete having a specific gravity of lower than 1.0.
As a process of increasing the physical performance of light-weight concrete, a polymer-impregnated concrete has been proposed. According to the process, a base material for light-weight concrete is impregnated with a vinyl monomer and the vinyl monomer is polymerized. The mechanical strength of the light-weight concrete obtained by such a process is remarkably higher than that of a concrete made of the base material as well as the elasticity, the chemical resistance, the freezing and thawing resistance, etc., of the concrete are improved but the polymer-impregnated concrete obtained by the above-described process has various problems in the producibility. That is, first, for effectively increasing the strength of the polymer-impregnated concrete, it is required to previously dry the base material so that the water content thereof is below 0.5%. Second, a radiation is required for the polymerization of a monomer impregnated in the concrete and it the polymerization of the vinyl monomer in the concrete is performed by a thermal polymerization, the loss of the vinyl monomer becomes large, which is uneconomical. Third, the working step for producing the concrete is complicated. These factors increase the production cost of the polymer-impregnated concrete and refuse the practical employment of the process.